Radio frequency (RF) scanning techniques are well known in the art allowing a two-way radio transceiver to scan a plurality of channelized frequencies in order to detect voice and/or data traffic on a channel. The original concept of channel scanning was to loop through a list of channels in order to check for activity. In the realm of public safety two-way radio communications, first responders work on a basic deployment system via a dispatcher where public safety personnel typically hear any communications by the dispatcher. This requirement has led to a “priority” type channel scan such that even if the transceiver receives audio communications from a different channel, it would always revert back to the dispatcher channel to ensure there is no activity.
The problem with this “priority scan” technique, especially on the conventional analog radio products, is that users desire to place a different importance on the priority channel. There are currently two types of priority scans utilized in the prior art. The priority scan technique in many analog products provides for a loop through the scan list where extra time is spent only looking back at the priority channel once the channel is unmuted on a non-priority channel. This type of approach means that the priority channel is scanned an equal amount as any other channel and only gets extra scan time once the transceiver is unmuted on a different channel. Similarly, the second type of priority scan that is utilized on many digital radio products provides a method where the scan loops or cycles through a scan list and then checks the priority channel after each individualized channel scan. Thus, using this method, the priority channel is scanned 50% of the time which will take the transceiver longer to move through the scan list. Moreover, there is an increased chance of “audio holes,” which are situations where the user misses audio on a non-priority channel since the scan misses audio segments as the receiver jumps from channel to channel.
Prior art FIG. 1 represents the first priority scanning process where the scanning method 100 is initiated 101 and a determination is made if channel activity 103 is present on a scanned channel. Qualified activity is defined as that threshold of activity such as voice or data traffic defined by the user that is intended for receipt while unqualified activity is not intended for receipt. If non-qualified activity is identified 105, then the radio will need to identify if the same channel has had unqualified activity for at least a predetermined number of scanning cycles or loops 119. Then the scanning algorithm will mark the channel such that the scan algorithm will not try to identify qualified activity until no activity is detected on the channel, y number of seconds, or z number of loops 115 through the scan list as it continues the normal unweighted scan 117. If qualified activity is identified 105, then the radio will unmute to the channel 121. Once unmuted to the active channel, the radio also checks for activity on a priority channel 107. If the priority channel has qualified activity 109 then the radio will switch to the priority channel and not start until the call or communications ends 113. If qualified activity is not detected, the transceiver continues unmuting to the channel until the call has ended or the priority channel has qualified activity. Thereafter, the unweighted (unmarked) channel behavior is continued 117 and the process starts over 101.
The second priority scanning process is shown in prior art FIG. 2 and utilizes a statically weighted priority scanning behavior where priority channel(s) are statically defined and their weight does not change during the scanning process. The radio loops through a scan list in an alternating format such that every other channel that is scanned is the priority channel. This effectively weights the priority channel(s) to 50% of the scanning activity. This behavior does not change based on channel activity. Like the priority scanning behavior noted above, this constant checking back to a priority channel causes the audio holes in the received audio. The flow chart illustrates the process 200 where the scanning process begins 201 and the priority channel is scanned followed by the first channel, then the priority channel, the second channel and then the priority channel etc. 203. If qualified activity is detected on a non-priority channel 205, the non-priority channel is unmuted 207. If the priority channel has qualified activity 209 then the radio switches from the previously unmuted channel to the priority channel and un-mutes and discontinues scanning 211. Scanning is initiated 213 when the call is completed. Thereafter, scanning sequence is again initiated 203. If non-qualified activity is detected on the priority channel while qualified activity exists on a non-priority channel 209, the radio continues the priority weighted scan behavior 215 and un-mutes to the non-priority channel 207. In the event where no qualified activity is detected on the non-priority channel 205, then the channel is marked as having unqualified activity until the carrier is no longer present, a predetermined time period has expired, or a predetermined number of loops through the scan list 217, and the radio continues the priority weighted scan behavior. Thereafter, the scanning process begins anew 201. Both of these scan solutions are well known; however, neither fully meets market needs in view of the possibility of missing priority information in the first process or the presence of audio holes left by continually cycling back to the priority channel in the second process.
Consequently, the need exists to provide for a scanning technique that will not only effectively scan through a channel list in a timely manner but will also be able to check for traffic on priority channels with reduced priority channel effects like voice holes or the like. The new process should utilize these concepts to adaptively adjust the scanning behavior based upon audio traffic.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.